820-3115 Dead

[jamiehorn1]

Hi all,

I have an 820-3115 that is completely dead.

This is the history so far:

- No green light and 9 volts on pubs_g3h

- Replaced ISL6259 because it looked like it had a hole in it

- Green light restored

- Powered up normally.

I then plugged it back into the power supply and Q7085 started burning up then the whole thing died, so i replaced it and now i get nothing.

No green light, no voltage anywhere, on the power supply it just defaults to 2v and 1.14 amps.

I assume the PCH and SMC are okay as it did power on but now i have no idea.

I tried to inject voltage on the DC in fuse but again defaults to 2v and 1.14 amps.

PP3V42 Resistance to ground = 041.8 ohms
PPBUS_G3H Resistance to ground = 000.5 ohms --> i assume this is the problem but how can i check whats shorted if I can’t inject voltage?

Any ideas?

 

[dukefawks]

ISL is dead again. Replace ISL Q7080/85 and Q7030/35. Also check R7005 and resistance between pins 17/18 27/28 on U7000.

 

[jamiehorn1]

Thanks Duke - will get to it tomorrow??

 

[jamiehorn1]

Okay so replaced all of those and i have 16v coming in and green light - but drawing 0 amps and PPBUS_G3H is only 0.1v

Any idea what to do next? it seems ISL is not creating the 12v but it's been replaced twice now

 

[jamiehorn1]

Current sensing seems fine too - Pins 27/28 are 20.3 ohms and 17/18 are 3 ohms (might be a bit high?)

 

[dukefawks]

Resistance to GND on PPBUS? ISL soldered correctly? R7005 checked?

 

[jamiehorn1]

Resistance to ground on PPBUS is 400k approx System side and 600k the other. ISL looks good and R7005 measures and looks okay too. Confused.com?

 

[dukefawks]

Check if 16V is present on R7020. If it is present you probably have bad soldering somewhere or killed the ISL.

 

[jamiehorn1]

Okay thanks Duke - I’ll leave it at that and close this??